Methods of inhibiting corrosion with condensed polyalkylenepolyamine phosphonates

ABSTRACT

Condensed polyalkylenepolyamine derivatives having the formula WHEREIN R1, R2, R3, R4, R5, X and Y are hereinafter defined, n is 1 - 15 and m is 1 - 20, alone or in combination with zinc, dichromate, certain thiols and 1,2,3-triazoles and mixtures thereof, are disclosed as inhibiting the corrosion of metals by oxygen-bearing waters.

United States Patent 1 King et al.

in] 3,714,067 1 Jan. 30,1973

1 1 METHODS OF INHIBITING CORROSION WITH CONDENSED POLYALKYLENEPOLYAMINE PHOSPHONATES Inventors: Thomas M. King, St. Louis; Robert S. Mitchell, Webster Groves, both of Mo.

Assignee: Monsanto Company, St Louis, Mo.

Filed: July 7, 1971 Appl. No.: 160,550

U.S. Cl ..252/389 A, 21/2.7, 210/58, 252/181, 252/387, 252/389 R, 260/5025 Int. Cl ..C23f 11/10, C231 11/16 Field of Search ..252/389 A, 387, 181, 389 R; 2l/2.7, 2.5; 260/5025; 210/58 References Cited UNITED STATES PATENTS 12/1959 Ramsey et al. ..260I502.5 11/1960 Bersworth et al. ..260/502.5 12/1964 Toy et a1. ..260/502.5

1/1967 lrani et al. ..260/502.5 10/1967 Lyons et a1. ..260/502.5

7/1968 lrani et a1. ..260/502.5

3,395,1 13 3,431,217 3/1969 Hwa ..252/3'87 3,483,133 12/1969 Hatch et al. .,...252/389 R Primary ExaminerLeon D. Rosdol Assistant Examiner1rwin Gluck Attorney-James .Iv Mullen et al.

[57] ABSTRACT Condensed polyalkylenepolyamine derivatives having the formula 20 Claims, No Drawings METHODS OF INHIBITING CORROSION WITH CONDENSED POLYALKYLENEPOLYAMINE PHOSPHONATES ln the Formula I, R,, R,, R, and R are alike or unlike and are from the group of radicals The present invention relates to corrosion inhibiting 5 (m X 0 compositions and to methods of inhibiting the corro- I ll sion of metal surfaces in contact with an aqueous medi- C P OM um of a corrosive nature. More particularly, this inven- Y M tion relates to methods of inhibiting the corrosion of (m) H 0 metal surfaces by utilizing in the corrosive aqueous l0 g and medium a condensed polyalkylenepolyamine deriva- I tive either alone or in combination with a water-soluble s 1 m M zinc salt, a dichromate, certain thiols, 1,2,3-triazoles (Iv) f H and mixtures thereof. C( J0H The present invention has special utility in the i; prevention of the corrosion of metals which are in coni m i h at least two Y)156 M" tact with circulating water, that is, water which is movgroups are present at ll times d are i h R d R ing through condensers, engine jackets, cooling towers, R 4 d R evaporators or distribution systems, however, it can be I formula 1 R i an lk l group tai i f one used to prevent the corrosion of metal surfaces in other to 20 f bl one to eight carbon atoms u as aqueous corrosive media. This invention is especially methypethyhpmpyl and the like, valuable in inhibiting the corrosion of ferrous metals in- In f l 1 and (pal-53]) Formula I], X and Y are cluding iron and steel (also galvanized steel) and nonh ik or unlike and are f m the group hydmge'n' ferrous metals including pp and its y and alkyl containing from one to eight, preferably one minum and its alloys and brass. These metals are to f carbon atoms 7 generally used in circulating water Systemsln formula I, n has a value of from 1 through 15 an The major corrosive ingredients of aqueous cooling m is from 1 through Systems are Primarily dissolved Oxygen and inorganic In formula 1 and (partial) Formula II and III, M is a salts, such as the carbonate, bicarbonate, chloride metal or hydrogen or any cation'which m yield and/or sulfate Salts of calcium magnesium and/0" sufficient solubility for the desired end-use. The aforementioned metal ions are from the group of metals al- It E therefore 'm F Q of mvemlon to kali metals such as sodium, lithium, potassium, alkaline provfde new F earth metals such as calcium and magnesium, alult is another ob ect of this invention to provide new minum, Zinc, cadmium, manganese nickel, cobalt, corrosion inhibiting methods for ferrous metals mclud- Cerium lead, tin, iron chromium, and mercury Also mg lI'OIl and steel and non-ferrous metals including included are ammonium ions and alkyl ammonium and brass ions. In particular, those alkyl ammonium ions derived It ls i of thls mventlon to provide f from amines having a low molecular weight, such as and corrosion inhibiting methods for ferrous metals m- 40 b 610 w about 300, and more particularly the alkyl cludmg and sieel and nonjfirmus metals Including amines, alkylene amines, and alkanol amines containprpepdgzir'n and brass in contact wit an aqueous corrosive ing not more than two amine groups such as ethyl It is another object of this invention to provide new 33 z p zg propgline corrosion inhibiting methods for ferrous metals includi l l i a g 1 T y i f f ing iron and steel and non-ferrous metals including ty f f l t in copper and brass in contact with cooling waters. preferred iq t e a t at t e Other advantages and objects of the present invenpm meta lonsl are t r-ender the tion will be apparent from the following discussion and pounfi a water'solub 6 Salt Sodlum' appended claims v I It is to be understood that all of the compounds It has been found that Certain condense d polyal falling within the above Formula land as heretof kylenepolyamine derivatives corresponding to the foldefined g genencauy i d herem as lowing formula polyamlne or polyamlnes. In other words then, the acids, salts and m xtures thereof are-all generically (I) R! x x R4 described herein as polyamines. I

l$fi Illustrative (but without limitation'lof some of the L Li L i v present invention corrosion inhibitors are shown below.

unexpectedly function as corrosion inhibitors when (I) B; used alone or in combination with zinc, dichromate', I certain thiols and 1,2,3-triazoles and mixtures thereof 2 \Y :1 L \Y/n R5 Compound No. R1 R2 3 R4 Rs X Y n m.

1 CH2PO3H2 -CH2PO:4H2 CH2PO:H2 CH2PO3H2 H H 3 l 2 Same as above Same as above. Same as above- Same as above;. H H 6 1 3. do.. .do.. do. do.. H- H 12 1 4. do -do.. .do H H 3 I 8 6. .do .do.. do H H 3 15 6.... 4311200011- CH1COOH ...do- H H- a -1 7 Same as above Same as above do ..do .do H H 6 1 2 in aqueous or water systems containing metals or in contact with metals.

Continued Compound No. R1 R2 lt; R, R X Y n 'm.

H 'l-I 12 1 H H 3 8 ..do ..do H H 3 l5 CH2PO3H2 CH2PO3H2 ..d0 H H 3 1 Same as above Same as above ..do Same as above H H 6 1 CH2CH:OH -CH2CHzOH CH2PO3H:.. H H 3 1 Same as above. Same as above Same as above H- H 6 1 do. ..do.. do..... H H 12 8 ..do.. do. H H 3 15 d H H 3 1 -CHZPOJH2 H H 3 1 Same as above Same as above-.. Same as above H H 6 1 CH2PO:N82. 2POsNaz- CH2PO3NB2 H H 3 1 Same as above Same as above. Same as above. H H 6 1 CHzPO;(NH4)-.. CHPO2(NH H H 3 1 CH2POaZXl H H 6 1 CH2POsN82- H H 3 1 CHgPO I-I2 -CH2PO3H2 .d0.... CH2PO3H2 CH2PO3H2 H H 15 The polyamines falling within the aforegoing Formula I are prepared according to thedisclosure set forth in my copending patent application Ser. No. 160,545, July 7, l971 filed concurrently herewith and which is incorporated herein by reference.

It has been found that to effectively inhibit corrosion, at least 3 parts per million, preferably from about 10 parts per million (ppm) to about 500 parts per million, more preferably from about 10 parts per million to about 150 parts per million, of the polyamine should be utilized in the corrosive medium. It is to be understood that greater than 500 ppm of polyamine can be utilized where one so desires as long as the desired end result is substantially achieved or these higher amounts are not detrimental to the water system. Amounts as low as 1 ppm are found to be effective.

The polyamine corrosion inhibitors of the present invention are effective in both an acidic or basic corrosive media. The pH can range from about 4 to about 12. For example, compound No. l, heretofore set forth, when used in amounts from about 3 parts per million to about 100 parts per million is an effective corrosion inhibitor in a corrosive medium where the pH is from about 4 to about 12.

In conjunction with the utilization of the polyamine per se as corrosion inhibitors, it has also been found that there exists a synergistic effect on corrosion inhibition between the polyamine and the zinc ion; that is, the use of the polyamine with the zinc ion more effectively inhibits corrosion than does an equal concentration of the polyamine or the zinc ion alone. (The zinc ion is used in approximately the same molar concentration as the polyamine, e.g., a suitable corrosion inhibitor may consist of 10 ppm of zinc ion. plus ppm of 50 said polyamine.) It is to be understood, then, that the present invention also encompasses a corrosion inhibition composition containing a mixture of the polyamine and a zinc-containing material (i.e., a water-soluble zinc salt) which is capable of forming the zinc ion in an aqueous solution.

Illustrative examples of the zinc-containing material (water-soluble zinc salt) which are set forth for exemplary purposes only and hence non-restrictive, include zinc acetate, zinc bromate, zinc benzoate, zinc borate, zinc bromide, zinc butyrate, zinc caproate, zinc carbonate, zinc chlorate, zinc chloride, zinc citrate, zinc fluoride, zinc fluosilicate, zinc formate, zinc hydroxide, zinc d-lactate, zinc laurate, zinc permanganate, zinc nitrate, zinc hypophosphite, zinc salicylate, zinc sulfate and zinc sulfite. The preferred water-soluble zinc salt is zinc sulfate. It is to be understood that it is within the scope of the present invention that the zinc ion can be suppl ied in part or wholly by using the zinc salt of the acid form of the polyamine.

The polyamine and the zinc containing material, which is, in essence, a water soluble zinc salt, may be mixed as a dry composition and can be fed into a water system containing the metals heretofore described .to be protected. Such a composition having maximum synergism between the polyamine and the zinc ion containing material comprises from about 2 percent to about percent by weight of the water soluble zinc salt and from about 20 percent to about 98 percent by weight of the polyamine, all weights being predicated upon the total weight of the mixture. Preferably the weight of the composition comprises from about 10 percent to about 60 percent by weight of the water soluble zinc salt and from about 40 percent to about '7 percent by weight of the polyamine.

A combination of about 3 to 100 ppm of the polyamine and about 0.5 to about 100 ppm zinc ion will inhibit corrosion in most water systems; the most preferred concentration range is about 5 to 25 ppm polyamine and about 5 to 25 ppm zinc ion. It is to be understood, however, that those concentrations are not in any manner meant to limit the scope of the present invention.

It has also been found that synergism exists between the polyamine and chromate or dichromate. Because chromate and dichromate are each readily converted into the other by a change in pH, it is understood that both will be simultaneously present at most pHs, even though only one is mentioned.

Corrosion in most water systems may be inhibited by adding from about 1 to about 100 ppm of polyamine and from about 1 to about 100 ppm of the chromate or dichromate; preferably from about 5 to 25 ppm polyamine and from about 5 to 25 ppm chromate or dichromate is added. It is to be understood that larger amounts or smaller amounts of each material can be utilized if one so desires.

Suitable chromates for use in the composition and process of this invention include, for exemplary purposes only, sodium dichromate dihydrate, anhydrous sodium chromate, sodium chromate tetrahydrate, sodium chromate hexahydrate, sodium chromate decahydrate, potassium dichromate, potassium chromate, ammonium dichromate, and chromic acid. In other words, the chromium compound used is any water soluble hexavalent compound of chromium and is preferably an alkali metal chromate or dichromate heretofore described.

In most cases, an effective corrosion inhibition composition contains a mixture of from about 1 percent to about 60 percent and preferably from about percent to about 40 percent, of the water soluble inorganic chromate, based on the combined weight of the chromate and polyamine. The use of chromates per se is further described in U.S. Pat. No. 3,431,217 and the publications cited in this patent, all of which are incorporated herein by reference.

It has also been found that compositions of the polyamine, zinc ion, and chromate or dichromate are useful in inhibiting the corrosion of metals. The inhibiting action of zinc (supplied in the form of a water soluble zinc salt heretofore mentioned) and dichromate compositions has been shown in U.S. Pat. No. 3,022,133, which is incorporated herein by reference. Thus, all three components of this composition are mutually synergistic. The coaction of zinc and dichromate illustrated in U.S. Pat. No. 3,022,133 remains unaffected in the presence of the polyamine and the other ingredients of the inhibitor compositions mentioned herein. In other words, then, it is within the scope of the present invention to provide a corrosion inhibiting composition containing the polyamine, a water soluble zinc salt and a chromate and/or dichromate.

Especially useful combinations of polyamine, chromate and zinc exist in the range of from about 1 to about 100 ppm of polyamine, from about A to about 50 ppm of the chromate or dichromate, and from about A to 50 ppm of the zinc ion. The preferred range is from ppm chromate or dichromate, and from about 1 to about ppm zinc ion.

Where the water systems are in contact with copper per se or copper-containing metals, it is desirable to use, along with the polyamine (either alone or in combination with the zinc ion and/or dichromate or chromate), a 1,2,3-thiazoles or a thiol of a thiazole, an oxazole, or an imidazole as described respectively in U.S. Pat. Nos. 2,941,953; 2,742,369; and 3,483,133; all of which patents are incorporated herein by reference. These azoles are referred to herein as thiols and 1,2,3- thiazoles. These thiols and 1,2,3-thiazo1es are found effective in inhibiting the attack of the polyamine on copper.

The preferred 1,2,3-triazole is 1,2,3-benzotriazole of the formula The preferred thiols of a thiazole, an oxazole, or an imidazole are Z-mercaptothioazole 2-mercaptobenzoxazole and Z-mercaptobenzimidazole The amounts of thiol or 1,2,3-thiazole used will depend upon the particular water system. Where the water system containingcopper is an open or once through system from about 3 to about 100 ppm 99mm. 9 1 93 5 to 5 PW" thiol HM-" 9 and up to about 100 ppm zinc ion are generally satisfactory concentrations; preferably the concentrations are about 5 to 25 ppm polyamine, about 0.5 to 2 ppm triazole or thiol, and about 5 to 25 ppm zinc ion.

A dry composition may be made which may be fed into the water system containing copper. Such a composition would consist of about 20 percent to 90 percent polyamine; about 1 percent to 10 percentthiol or 1,2,3-triazole, and up to about 79 percent soluble zinc salt; preferably, it would consist of about 38 percent to 90 percent polyamine, about 2 percent to 10 percent thiol or 1,2,3-triazole, and up to about 60 percent soluble zinc salt.

It is within the scope of the present invention that the corrosion inhibitors of this invention may be used in conjunction with various well-known inhibitors such as the molecularly dehydrated phosphates and phosphonates (such as those disclosed in U.S. Pat. No. 3,483,133 which is incorporated herein by reference).

In conjunction with the Examples hereinafter set forth, two tests are conducted to determine the effectiveness of the corrosion inhibitors of the presentinvention in different corrosive media, i.e., ordinary tap water and synthetic cooling tower water.

Test 1 was conducted at room temperatures, about F, wherein several coupons of mild steel (S.A.E. 1018) having dimensions of 5 cm X 3.5 cm X 0.32 cm were thoroughly cleaned using a commercially available cleansing powder and rinsed with distilled water and acetone. After the coupons were weighed, they were mounted on brackets and continuously immersed and removed from the corrosion composition, i.e., ordinary tap water, so that the coupons remain immersed in the composition for 60 seconds and then remained out of solution, exposed to air for 60 seconds. This procedure was continued for a definite length of time (in hours) after which the coupons were withdrawn and the corrosion products on the coupons were removed by using a soft brush.

The coupons were rinsed with distilled water and acetone and then reweighed. The loss in weight (in milligrams) was then appropriately inserted into the equation:

KW/DA T= Corrosion in mills per year wherein W= weight loss during tests in milligrams;

D specific gravity of the metal;

A exposed surface area in square cm; and

T= time of exposure to solution in hours K 3402 in order to determine the corrosion that has taken place expressed in terms of mills of penetration per year (m.p.y.). The corrosion rate of the coupons protected by a corrosion inhibitor can then be compared to the corrosion rate of the unprotected coupons. A

decrease in the corrosion r ate indicates the effectiveness of the corrosion inhibitor.

In tests of this nature where the aqueous corrosive medium is ordinary tap water at room temperature, any corrosion rate less than that corrosion rate of the said medium is desired and rates of less than m.p.y. are highly desired and substances that give this value or lower are considered excellent. This does not mean, however, that substances having a corrosion rate of more than 5 m.p.y. are not valuable; depending upon the particular conditions a compound having a higher corrosion rate may be used, as in an instance where the equipment will be used, only for a short period of time.

A cooling water system was constructed on a small scale to approximate actual conditions for Test 2. From a five gallon glass tank containing synthetic cooling water, a hose leads into a 6 in. glass jacket which surrounds a mild steel pipe. A hose leads from the jacket into a glass condenser and then back to the tank. Air is added to the system at the condenser in order to match an actual operation in which air is absorbed by the cooling water. Steam is passed through the steel pipe which is enclosed by the glass jacket.

Four mild steel coupons were weighed and then mounted in the tank. After exposure the steel pipe was checked visibly for signs of corrosion and the corrosion rate of the coupons was calculated. Synthetic cooling water was prepared to approximate actual cooling water as follows:

Ca 200 ppm Mg 55 ppm Na 320 ppm Cl' 600 ppm S0,- 500 ppm HCO, 58 ppm Total Dissolved Solids of Distilled Water 1,733

A circulating cooling water system contains a high concentration of inorganic salt or ions much higher than ordinary tap water as can be seen from the formulation for synthetic cooling tower water. Likewise a cooling water system is operated at high temperatures usually 50 C or higher. Primarily because of these two factors the acceptable corrosion rates in cooling waters is less than 10 m.p.y. therefore, corrosion inhibitors having corrosion rates less than 10 m.p.y. are considered good and commercially acceptable.

The corrosion inhibiting compositions of this invention can be manufactured via a number of methods which will give good protection against corrosion. For example, the polyamine either in the form of its acid or salt per se or in combination with the water-soluble zinc salt, chromate, dichromate, thiols and 1,2,3- thiazole can simply be dissolved by intermixing them into the aqueous corrosive medium. Via another method, they can be dissolved separately in water or another suitable solvent and then intermixed into the aqueous corrosive medium.

Various means are available to insure that the correct proportion of corrosion inhibitor is present in the corrosive medium. For example, a solution containing the said corrosion inhibitor can be metered into the corrosive medium by a drip feeder. Another method is to formulate tablets or briquettes of a solid polyamine (and other ingredients) and these can then be added to the corrosive medium. The said solid," after briquetting, can be used in a standard ball feeder so that the solid is released slowly into the corrosive medium.

The invention will be further illustrated but is not limited by the following examples:

EXAMPLE I Three separate portions consisting each of 600 ml of aqueous corrosive medium are individually treated with the indicated polyamine so that it contains separately 5, 50 and 100 parts per million of polyamine. (Where the acid form is used, it is converted to the sodium salt by the addition of sufficient NaOl-l to maintain the medium at pH 9.0 to 9.5.) Test 1 as described hereinbefore is conducted using 1018 S.A.E. mild steel coupons measuring 5 cm X 3.5 cm X 0.32 cm. The corrosive medium is a sample of water obtained from the St. Louis County Water Company having a pH from about 9.0 to about 9.5 and a hardness of about 100 to about 1 10 parts per million as calcium carbonate. Test 1 is conducted according to the procedure hereinbefore outlined for hours. Six hundred ml. of the untreated aqueous corrosive medium is tested as a control. The data are illustrated in Table 1.

Test 1 is also conducted on a commercially available corrosion inhibitor, containing some zinc about 1 to about 4 percent by weight but mostly tetra sodium pyrophosphate about 40 to about 60 percent by weight; these data are shown in Table 1.

TABLE 1 Corrosion Rates on Mild Steel (S.A.E. 1018) Coupons 5 cm X 3.5 cm X 0.32 cm pH 9.0 to 9.5 ofthe Corrosive Media concencorrosion tration time Rate Corrosion Inhibitor ppm (hrs) (m.p.y.)

Corrosion Medium 96 25.2 Polyarnine Compound No.

1 5 96 8.1 1 5O 96 4.7 1 100 96 2.2 2 S 96 10.1 2 50 96 8.4 2 100 96 5.2 4 5 96 4.7 4 50 96 2.6 4 100 96 2.0 6 5 96 9.7 6 50 96 4.4 6 100 96 3.8 13 5 96 1 1.5 13 S0 96 5.0 13 100 96 4.2 18 5 96 6.9 18 50 96 3.9 18 100 96 3.0 20 5 96 8.2 20 50 96 4.6 20 100 96 2.8 22 5 96 l 1.3 22 50 96 6.3 22 100 96 3.4 Corrosion Medium 96 29.6 Zinc Tetra Sodium Pyrophosphate (Zinc 1% 5 96 15 4%, tetra sodium pryo- 5O 96 6.8 phosphate 40% to 60% 100 96 4.1

The data in Table 1 show that the polyamines are an effective corrosion inhibitor. Table 1 shows that these polyamines are at least as good as and in some cases superior to the commercially available zinc tetra sodium pyrophosphate inhibitor. As pointed out before, substances that reduce the corrosion rates of mild steel to less than m.p.y. in ordinary tap water are considered excellent. Therefore, it can readily be appreciated that the polyamines of the present invention are effective corrosion inhibitors.

EXAMPLE II Test 2, as described hereinbefore, is conducted to determine the effectiveness of the indicated polyamine (Example I) as a corrosion inhibitor in cooling water. The polyamines are added to the five gallon tank containing about 16,000 ml. of synthetic cooling tower water (having a flow rate of 2,640 ml./min.), as set forth above, so that said water contains 5, 50, and 100 parts per million of the polyamine. The temperature of the synthetic cooling water is 50 C. Mild steel coupons (ASTM A-285) measuring 2.5 cm X 5 cm X .6 cm are cleaned with a commercially available cleansing powder and weighed. They are then mounted on brackets in the five gallon tank. After exposure, they are reweighed and their corrosion rates are calculated.

A blank solution containing no polyamine is used as a control to determine the corrosion rates of mild steel coupons in untreated synthetic cooling tower water.

The data show that the polyamine corrosion inhibitors at greater than 50 ppm reduce the corrosion rate to less than m.p.y. (the control corrosion medium is about 24.6 m.p.y.), which is the generally acceptable rate for a corrosion inhibitor.

A visual inspection of the mild steel pipe through which the steam passes and which is cooled by the synthetic cooling water treated with polyamine shows a very minute amount of corrosion, another indication of the effectiveness of the novel compound of the present invention.

A commercial corrosion inhibitor containing 2 percent to 4 percent by weight of zinc and 40 percent to 60 percent by weight of tetra sodium pyrophosphate, is used to treat the synthetic cooling water and is tested in the same manner as Example II. The corrosion rates of the coupons are more than 10 m.p.y. and a significant amount of corrosion forms on the mild steel pipe through which the steam passes.

It can readily be appreciated that these polyamines are good corrosion inhibitors when used in cooling waters and especially when used in heat-exchanging systems.

EXAMPLE III Example l (above) is repeated with the exception that in addition to the polyamine (5, 50 and 100 ppm) corrosion inhibitor, there is added sufficient amounts of zinc sulfate in order to provide respectively 5, 50 and 100 ppm of zinc ion in the corrosion medium. The synergistic corrosion inhibitor, i.e., the indicated polyamine plus the zinc sulfate, shows that at all three concentrations (i.e., 5, 50 and 100 ppm of each) the corrosion rates are substantially less than the rates using the corrosion medium without this mixture and is on the average 25 percent less than those rates obtained using only the polyamine per se.

EXAMPLE IV Example I (above) is repeated with the exception that in addition to the polyamine (5,50 and 100 ppm) corrosion inhibitor, there is added respectively 5, 50 and ppm sodium dichromate to the corrosion medium. The synergistic corrosion inhibitor, i.e., the indicated polyamine plus the sodium dichromate, shows that at all three concentrations (i.e., 5, 50 and 100 ppm of each), the corrosion rate is less than the rate using the corrosion medium without this mixture and is on the average about 14 to 21 percent less than those rates obtained using only the polyamine per se.

EXAMPLE V A series of separate and individual corrosion inhibitors consisting of a mixture of the indicated polyamine (60 percent by weight), zinc sulfate (20 percent by weight) and sodium dichromate (20 percent by weight) arevprepared. Example I (above) is then repeated utilizing the above mixture. The resultant data shows that the corrosion rates using this mixture are substantially less than the rates using the corrosion medium without this mixture and is on the average about 31 percent to 41 percent less than those rates obtained using only the polyamine per se.

EXAMPLE VI The corrosion inhibitors as described in the above Examples I, III, IV and V are separately and individually tested in boiler water for their separate corrosive inhibiting effect on red brass and mild steel. The boiler water contains approximately 30-60 parts per million phosphate and approximately 30-60 parts per million sulfate having a pH of about 14. The corrosive tests are carried out at a temperature of 314 C at 1500 psig and with a 50 parts per million of the respective corrosion inhibitor. In each test, approximately 1 liter of boiler blow-down water is charged into a 2 liter bomb and 1 ml. of a stock solution is added to give approximately 50 parts per million of the corrosion inhibitor. Duplicate coupons of mild steel and red brass measuring 5 cm X 3.5 cm X 0.32 cm are scrubbed with a commercially available cleansing powder and weighed. The coupons are then mounted on insulated brackets so that two coupons are in the liquid phase and two coupons are in the vapor phase. After sealing the bomb, the cycle of pumping down with a vacuum pump and filling with nitrogen is repeated four times. The time of the tests are taken to be roughly from the time the temperature reached C after starting to heat till it again reached this temperature after turning off the heat.

The results of these tests show that at temperatures above 300 C. the respective corrosion inhibitors significantly reduces the corrosion rates of both red brass and mild steel either completely immersed in the cooling waters or in contact with the vapors of a cooling water system containing the complex. It also demonstrates the stability of the corrosion inhibitors of the present invention at elevated temperatures, over 300 C, for extended periods of time.

In each of the following examples, the indicated polyamine and zinc compound are added to the aqueous corrosive medium so that 50 parts per million of each is present.

Zinc sulfate 2 EXAMPLE VIII Ingredients Parts Aqueous corrosive medium 80,000 Polyamine Compound No. 2 2.6 Zinc sulfate 2.6

EXAM PLE IX Ingredients Parts Aqueous corrosive medium 90,000 Polyamine Compound No. 6 2.3 Zinc sulfate 23 EXAMPLE X Ingredients Parts Aqueous corrosive medium 90,000 Polyamine Compound No. 13 2.3 Zinc sulfate 2.3

EXAM PLE XI Ingredients Parts Aqueous corrosive medium 90,000 Polyamine Compound No. 14 2.3 Zinc sulfate 2.3

EXAM PLE XII Ingredients Parts Aqueous corrosive medium 65.000 Polyamine Compound No. l8 1.6 Zinc sulfate 1.6

EXAMPLE XIII Ingredients Parts Aqueous corrosive medium I 1,000 Polyamine Compound No. 20 2.7 Zinc sulfate 2.7

EXAM PLE XIV Ingredients Parts Aqueous corrosive medium 100,000 Polyamine Compound No. 22 2.5 Zinc sulfate 2.5

(The sodium salts of the above Compound Nos. 1, 2, 6, 13, 14 and 18 are used in place of the acid forms.)

Tests 1 and 2 were conducted on each of the abovetreated aqueous corrosive media. The corrosion rates in all instances were lower than the untreated corrosive media. These Examples are repeated with the exception that the zinc salt used in zinc chloride (in one repeat) and zinc acetate (in another repeat). Similar results are obtained in both cases as compared to the results obtained using zinc sulfate.

EXAMPLE XV A compressed ball of a standard weight and dimension is prepared containing the following ingredients in the quantities noted.

Polyamine Compound No. l 34 Lignosulfite binder (bindarene) 8 Zinc sulfate 16 Inert Ingredients 42 The above composition after briquetting is found suitable for mechanically measured addition in water treatment wherein a ball feeder is employed.

EXAMPLE XVI Example I (above) is repeated with the exception that copper coupons are used instead of mild steel coupons and sufficient amounts of l,2,3-benzotriazole to provide 1, 5 and 10 ppm thereof in the corrosive media is used in addition to the polyamine. Example XVI is repeated again but without the benzotriazole material. The data shows that when copper coupons are used and the corrosive media contains the indicated polyamine, the corrosion rates are less than when the corrosion media does not contain said polyamine. The data further show that use of the benzotriazole with the polyamine further reduces the corrosion rate.

It is also within the scope of the present invention to utilize silicates, particularly inorganic silicates, in combination with the polyamines. It is known that silicates are effective corrosion inhibitors as exemplified by Encyclopedia of Chemical Technology," Kirk- Othmer, 1961 by The Interscience Encyclopedia, Inc. New York Volume 4, pages 487-529, and Volume 12, pages 268-360; this subject matter is to be considered as incorporated herein by reference. (These silicates can be used in the same concentration as the watersoluble zinc salts heretofore mentioned.)

It is found in the repeat of the above Example I that the use of a combination of the indicated polyamine and a liquid (sodium) silicate (having a 3.22:1 ratio of SiO to soda) effected a lower corrosion rate than either the polyamine per se or the silicate per se when used separately.

Thus, it may be seen that this invention relates to the indicated polyamines falling within Formula I above as corrosion inhibitors. We do not intend to be limited to any compounds, composition, or methods disclosed herein for illustrative purposes. Our invention may be otherwise practiced and embodied within the scope of the following claims.

What is claimed is:

l. A composition useful for inhibiting the corrosion of metals in a water system consisting essentially of from about 2 percent to about percent by weight of a water soluble zinc salt and from about 20 percent to 98 percent by weight of a polyamine having the general formula 3 ac Ella? 1 R. W. lAl/J...

wherein (a) R R R and R are alike or unlike and are each selected from the group consisting of wherein M is either hydrogen or any cation which will i provide sufficient solubility in said aqueous system; (b) R is an alkyl group containing from about one to eight carbon atoms; (0) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl; (d) n has a value of from 1 through and (e) m has a value of from 1 through with the proviso that said polyamine has at least two C(X)(Y)PO M groups at all times and are either R and R or R and R 2. The composition as set forth in claim 1 wherein X and Y both are hydrogen.

3. The composition as set forth in claim 2 wherein R R R and R are each ---CH PO,,M groups.

4. The composition as set forth in claim 2 wherein M is a cation selected from the group consisting of alkali metals, ammonia, zinc, and mixtures thereof.

5. The composition as set forth in claim 4 wherein the water soluble zinc salt is zinc sulfate and M is sodi 6. The composition as set forth in claim 1 and additionally containing a water-soluble hexavalent compound of chromium.

7. A composition useful for inhibiting the corrosion of metals in a water system which contains cuprous metals consisting essentially of (1) from about 20 percent to about 90 percent by weight of a polyamine having the general formula wherein (a) R,, R R and R are alike or unlike and are each selected from the group consisting of -fE-E-OM, and J IOH R, is an alkyl group containing from about one to eight carbon atoms; (c) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl; (d) n has a value of from 1 through 15 and (e) m has a value of from 1 through 20; with the proviso that said polyamine polyphosphonate has at least two C(X)(Y)PO M groups at all times and are either R and R or R and R (2) from about 1 percent to about 10 percent by weight of a compound selected from the group consisting of 1,2,3-triazoles, thiols of thiazoles, thiols of oxazoles, thiols of imidazoles, and mixtures thereof, and (3) up to about 79 percent by weight of a water soluble zinc salt.

8. The composition as set forth in claim 7 wherein said polyamine is selected from the group consisting of H203PH2C CHzPOgHz HzOaPHgC CHzPOzHz Ha z OaHz sodium salts thereof and mixtures thereof.

9. The composition as set forth in claim 7 and additionally containing a water-soluble hexavalent compound of chromium.

10. A method of inhibiting the corrosion of metals in a water system comprising maintaining in the water of said system at least 3 parts per million of a polyamine having the general formula wherein (a) R R R and R are alike or unlike and are each selected from the group consisting of wherein M is either hydrogen or any cation which will provide sufficient solubility in said aqueous system (b) R is an alkyl group containing from about one to eight carbon atoms; (c) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl; (d)n has a value of from 1 through 15 and (e) m has a value of from 1 through 20; with the proviso that said polyamine has at least two -C(X)(Y)PO,M,

groups at all times and are eitherR, and R or R and R 11. The composition as set forth in claim wherein X and Y both are hydrogen.

12. The composition as set forth in claim 11 wherein R R R and R are each Cl-l PO -,M groups.

13. The composition as set forth in claim 11 wherein M is a cation selected from the group consisting of alkali metals, ammonia, zinc, and mixtures thereof.

14. The method as set forth in claim 10 and additionally containing in said system a water soluble hexavalent compound of chromium.

15. The method as set forth in claim 10 and additionally containing in said system a water soluble zinc salt 16. The method as set forth in claim 15 and additionally containing in said system a water soluble hexavalent compound of chromium and a water soluble zinc salt.

17. The method as set forth in claim 10 wherein said system contains cuprous metals and the water system additionally contains a compound selected from the group consisting of 1,2,3-triazoles, thiols of thiazoles, thiols of oxazoles, thiols of imidazoles, and mixtures thereof.

18. The method as set forth in claim 17 wherein the water system additionally contains a water soluble zinc salt.

19. A method of inhibiting metal corrosion in a water system containing metals comprising maintaining in the water of said system (a) from about 3 to about 100 ppm of methylimino bis-(propyl amino) tetra(methylene phosphonic acid), (H O PH C) N(CH N(CH (CH- N(Cl-l PO l-l or its water soluble salts and (b) up to about 100 ppm zinc ion derived from water soluwherein (a) R, R R and R are alike or unlike and are each selected from the group consisting of wherein M is either hydrogen or any cation which will provide sufficient solubility in said aqueous system; (b) R, is an alkyl group containing from about one to eight carbon atoms; (0) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl: (d) n has a value of from 1 through 15 and (e m has a value of from 1 through 20; with he proviso t at said polyamine has at least two C(X)(Y)P0 M groups at all times and are either R and R or R and R 

1. A composition useful for inhibiting the corrosion of metals in a water system consisting essentially of from about 2 percent to about 80 percent by weight of a water soluble zinc salt and from about 20 percent to 98 percent by weight of a polyamine having the general formula wherein (a) R1, R2, R4 and R5 are alike or unlike and are each selected from the group consisting of wherein M is either hydrogen or any cation which will provide sufficient solubility in said aqueous system; (b) R3 is an alkyl group containing from about one to eight carbon atoms; (c) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl; (d) n has a value of from 1 through 15 and (e) m has a value of from 1 through 20; with the proviso that said polyamine has at least two -C(X)(Y)PO3Mgroups at all times and are either R1 and R2 or R4 and R5.
 2. The composition as set forth in claim 1 wherein X and Y both are hydrogen.
 3. The composition as set forth in claim 2 wherein R1, R2, R4 and R5 are each -CH2PO3M2 groups.
 4. The composition as set forth in claim 2 wherein M is a cation selected from the group consisting of alkali metals, ammonia, zinc, and mixtures thereof.
 5. The composition as set forth in claim 4 wherein the water soluble zinc salt is zinc sulfate and M is sodium.
 6. The composition as set forth in claim 1 and additionally containing a water-soluble hexavalent compound of chromium.
 7. A composition useful for inhibiting the corrosion of metals in a water system which contains cuprous metals consisting essentially of (1) from about 20 percent to about 90 percent by weight of a polyamine having the general formula wherein (a) R1, R2, R4 and R5 are alike or unlike and are each selected from the group consisting of wherein M is either hydrogen or any cation which will provide sufficient solubility in said aqueous system; (b) R3 is an alkyl group containing from about one to eight carbon atoms; (c) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl; (d) n has a value of from 1 through 15 and (e) m has a value of from 1 through 20; with the proviso that said polyamine polyphosphonate has at least two -C(X)(Y)PO3M2 groups at all times and are either R1 and R2 or R4 and R5; (2) from about 1 percent to about 10 percent by weight of a compound selected from the group consisting of 1,2,3-triazoles, thiols of thiazoles, thiols of oxazoles, thiols of imidazoles, and mixtures thereof, and (3) up to about 79 percent by weight of a water soluble zinc salt.
 8. The composition as set forth in claim 7 wherein said polyamine is selected from the group consisting of
 9. The composition as set forth in claim 7 and additionally containing a water-soluble hexavalent compound of chromium.
 10. A method of inhibiting the corrosion of metals in a water system comprising maintaining in the water of said system at least 3 parts per million of a polyamine having the general formuLa wherein (a) R1, R2, R4 and R5 are alike or unlike and are each selected from the group consisting of wherein M is either hydrogen or any cation which will provide sufficient solubility in said aqueous system; (b) R3 is an alkyl group containing from about one to eight carbon atoms; (c) X and Y are each alike or unlike and are selected from the group consisting of hydrogen and alkyl; (d)n has a value of from 1 through 15 and (e) m has a value of from 1 through 20; with the proviso that said polyamine has at least two -C(X)(Y)PO3M2 groups at all times and are eitherR1 and R2 or R4 and R5.
 11. The composition as set forth in claim 10 wherein X and Y both are hydrogen.
 12. The composition as set forth in claim 11 wherein R1, R2, R4, and R5 are each -CH2PO3M2 groups.
 13. The composition as set forth in claim 11 wherein M is a cation selected from the group consisting of alkali metals, ammonia, zinc, and mixtures thereof.
 14. The method as set forth in claim 10 and additionally containing in said system a water soluble hexavalent compound of chromium.
 15. The method as set forth in claim 10 and additionally containing in said system a water soluble zinc salt.
 16. The method as set forth in claim 15 and additionally containing in said system a water soluble hexavalent compound of chromium and a water soluble zinc salt.
 17. The method as set forth in claim 10 wherein said system contains cuprous metals and the water system additionally contains a compound selected from the group consisting of 1,2,3-triazoles, thiols of thiazoles, thiols of oxazoles, thiols of imidazoles, and mixtures thereof.
 18. The method as set forth in claim 17 wherein the water system additionally contains a water soluble zinc salt.
 19. A method of inhibiting metal corrosion in a water system containing metals comprising maintaining in the water of said system (a) from about 3 to about 100 ppm of methylimino bis-(propyl amino) tetra(methylene phosphonic acid), (H2O3PH2C)2N(CH2)3N(CH3) (CH2)3N(CH2PO3H2)2, or its water soluble salts and (b) up to about 100 ppm zinc ion derived from water soluble zinc salts. 